1 /*
2 * (C) Copyright 2002 Linus Torvalds
3 * Portions based on the vdso-randomization code from exec-shield:
4 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
5 *
6 * This file contains the needed initializations to support sysenter.
7 */
8
9 #include <linux/init.h>
10 #include <linux/smp.h>
11 #include <linux/thread_info.h>
12 #include <linux/sched.h>
13 #include <linux/gfp.h>
14 #include <linux/string.h>
15 #include <linux/elf.h>
16 #include <linux/mm.h>
17 #include <linux/err.h>
18 #include <linux/module.h>
19
20 #include <asm/cpufeature.h>
21 #include <asm/msr.h>
22 #include <asm/pgtable.h>
23 #include <asm/unistd.h>
24 #include <asm/elf.h>
25 #include <asm/tlbflush.h>
26 #include <asm/vdso.h>
27 #include <asm/proto.h>
28
29 enum {
30 VDSO_DISABLED = 0,
31 VDSO_ENABLED = 1,
32 VDSO_COMPAT = 2,
33 };
34
35 #ifdef CONFIG_COMPAT_VDSO
36 #define VDSO_DEFAULT VDSO_COMPAT
37 #else
38 #define VDSO_DEFAULT VDSO_ENABLED
39 #endif
40
41 #ifdef CONFIG_X86_64
42 #define vdso_enabled sysctl_vsyscall32
43 #define arch_setup_additional_pages syscall32_setup_pages
44 #endif
45
46 /*
47 * This is the difference between the prelinked addresses in the vDSO images
48 * and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
49 * in the user address space.
50 */
51 #define VDSO_ADDR_ADJUST (VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)
52
53 /*
54 * Should the kernel map a VDSO page into processes and pass its
55 * address down to glibc upon exec()?
56 */
57 unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
58
vdso_setup(char * s)59 static int __init vdso_setup(char *s)
60 {
61 vdso_enabled = simple_strtoul(s, NULL, 0);
62
63 return 1;
64 }
65
66 /*
67 * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
68 * behavior on both 64-bit and 32-bit kernels.
69 * On 32-bit kernels, vdso=[012] means the same thing.
70 */
71 __setup("vdso32=", vdso_setup);
72
73 #ifdef CONFIG_X86_32
74 __setup_param("vdso=", vdso32_setup, vdso_setup, 0);
75
76 EXPORT_SYMBOL_GPL(vdso_enabled);
77 #endif
78
reloc_symtab(Elf32_Ehdr * ehdr,unsigned offset,unsigned size)79 static __init void reloc_symtab(Elf32_Ehdr *ehdr,
80 unsigned offset, unsigned size)
81 {
82 Elf32_Sym *sym = (void *)ehdr + offset;
83 unsigned nsym = size / sizeof(*sym);
84 unsigned i;
85
86 for(i = 0; i < nsym; i++, sym++) {
87 if (sym->st_shndx == SHN_UNDEF ||
88 sym->st_shndx == SHN_ABS)
89 continue; /* skip */
90
91 if (sym->st_shndx > SHN_LORESERVE) {
92 printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
93 sym->st_shndx);
94 continue;
95 }
96
97 switch(ELF_ST_TYPE(sym->st_info)) {
98 case STT_OBJECT:
99 case STT_FUNC:
100 case STT_SECTION:
101 case STT_FILE:
102 sym->st_value += VDSO_ADDR_ADJUST;
103 }
104 }
105 }
106
reloc_dyn(Elf32_Ehdr * ehdr,unsigned offset)107 static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
108 {
109 Elf32_Dyn *dyn = (void *)ehdr + offset;
110
111 for(; dyn->d_tag != DT_NULL; dyn++)
112 switch(dyn->d_tag) {
113 case DT_PLTGOT:
114 case DT_HASH:
115 case DT_STRTAB:
116 case DT_SYMTAB:
117 case DT_RELA:
118 case DT_INIT:
119 case DT_FINI:
120 case DT_REL:
121 case DT_DEBUG:
122 case DT_JMPREL:
123 case DT_VERSYM:
124 case DT_VERDEF:
125 case DT_VERNEED:
126 case DT_ADDRRNGLO ... DT_ADDRRNGHI:
127 /* definitely pointers needing relocation */
128 dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
129 break;
130
131 case DT_ENCODING ... OLD_DT_LOOS-1:
132 case DT_LOOS ... DT_HIOS-1:
133 /* Tags above DT_ENCODING are pointers if
134 they're even */
135 if (dyn->d_tag >= DT_ENCODING &&
136 (dyn->d_tag & 1) == 0)
137 dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
138 break;
139
140 case DT_VERDEFNUM:
141 case DT_VERNEEDNUM:
142 case DT_FLAGS_1:
143 case DT_RELACOUNT:
144 case DT_RELCOUNT:
145 case DT_VALRNGLO ... DT_VALRNGHI:
146 /* definitely not pointers */
147 break;
148
149 case OLD_DT_LOOS ... DT_LOOS-1:
150 case DT_HIOS ... DT_VALRNGLO-1:
151 default:
152 if (dyn->d_tag > DT_ENCODING)
153 printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
154 dyn->d_tag);
155 break;
156 }
157 }
158
relocate_vdso(Elf32_Ehdr * ehdr)159 static __init void relocate_vdso(Elf32_Ehdr *ehdr)
160 {
161 Elf32_Phdr *phdr;
162 Elf32_Shdr *shdr;
163 int i;
164
165 BUG_ON(memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0 ||
166 !elf_check_arch_ia32(ehdr) ||
167 ehdr->e_type != ET_DYN);
168
169 ehdr->e_entry += VDSO_ADDR_ADJUST;
170
171 /* rebase phdrs */
172 phdr = (void *)ehdr + ehdr->e_phoff;
173 for (i = 0; i < ehdr->e_phnum; i++) {
174 phdr[i].p_vaddr += VDSO_ADDR_ADJUST;
175
176 /* relocate dynamic stuff */
177 if (phdr[i].p_type == PT_DYNAMIC)
178 reloc_dyn(ehdr, phdr[i].p_offset);
179 }
180
181 /* rebase sections */
182 shdr = (void *)ehdr + ehdr->e_shoff;
183 for(i = 0; i < ehdr->e_shnum; i++) {
184 if (!(shdr[i].sh_flags & SHF_ALLOC))
185 continue;
186
187 shdr[i].sh_addr += VDSO_ADDR_ADJUST;
188
189 if (shdr[i].sh_type == SHT_SYMTAB ||
190 shdr[i].sh_type == SHT_DYNSYM)
191 reloc_symtab(ehdr, shdr[i].sh_offset,
192 shdr[i].sh_size);
193 }
194 }
195
196 static struct page *vdso32_pages[1];
197
198 #ifdef CONFIG_X86_64
199
200 #define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SYSENTER32))
201 #define vdso32_syscall() (boot_cpu_has(X86_FEATURE_SYSCALL32))
202
203 /* May not be __init: called during resume */
syscall32_cpu_init(void)204 void syscall32_cpu_init(void)
205 {
206 /* Load these always in case some future AMD CPU supports
207 SYSENTER from compat mode too. */
208 checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
209 checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
210 checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
211
212 wrmsrl(MSR_CSTAR, ia32_cstar_target);
213 }
214
215 #define compat_uses_vma 1
216
map_compat_vdso(int map)217 static inline void map_compat_vdso(int map)
218 {
219 }
220
221 #else /* CONFIG_X86_32 */
222
223 #define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SEP))
224 #define vdso32_syscall() (0)
225
enable_sep_cpu(void)226 void enable_sep_cpu(void)
227 {
228 int cpu = get_cpu();
229 struct tss_struct *tss = &per_cpu(init_tss, cpu);
230
231 if (!boot_cpu_has(X86_FEATURE_SEP)) {
232 put_cpu();
233 return;
234 }
235
236 tss->x86_tss.ss1 = __KERNEL_CS;
237 tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
238 wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
239 wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
240 wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
241 put_cpu();
242 }
243
244 static struct vm_area_struct gate_vma;
245
gate_vma_init(void)246 static int __init gate_vma_init(void)
247 {
248 gate_vma.vm_mm = NULL;
249 gate_vma.vm_start = FIXADDR_USER_START;
250 gate_vma.vm_end = FIXADDR_USER_END;
251 gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
252 gate_vma.vm_page_prot = __P101;
253
254 return 0;
255 }
256
257 #define compat_uses_vma 0
258
map_compat_vdso(int map)259 static void map_compat_vdso(int map)
260 {
261 static int vdso_mapped;
262
263 if (map == vdso_mapped)
264 return;
265
266 vdso_mapped = map;
267
268 __set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
269 map ? PAGE_READONLY_EXEC : PAGE_NONE);
270
271 /* flush stray tlbs */
272 flush_tlb_all();
273 }
274
275 #endif /* CONFIG_X86_64 */
276
sysenter_setup(void)277 int __init sysenter_setup(void)
278 {
279 void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
280 const void *vsyscall;
281 size_t vsyscall_len;
282
283 vdso32_pages[0] = virt_to_page(syscall_page);
284
285 #ifdef CONFIG_X86_32
286 gate_vma_init();
287 #endif
288
289 if (vdso32_syscall()) {
290 vsyscall = &vdso32_syscall_start;
291 vsyscall_len = &vdso32_syscall_end - &vdso32_syscall_start;
292 } else if (vdso32_sysenter()){
293 vsyscall = &vdso32_sysenter_start;
294 vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
295 } else {
296 vsyscall = &vdso32_int80_start;
297 vsyscall_len = &vdso32_int80_end - &vdso32_int80_start;
298 }
299
300 memcpy(syscall_page, vsyscall, vsyscall_len);
301 relocate_vdso(syscall_page);
302
303 return 0;
304 }
305
306 /* Setup a VMA at program startup for the vsyscall page */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)307 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
308 {
309 struct mm_struct *mm = current->mm;
310 unsigned long addr;
311 int ret = 0;
312 bool compat;
313
314 #ifdef CONFIG_X86_X32_ABI
315 if (test_thread_flag(TIF_X32))
316 return x32_setup_additional_pages(bprm, uses_interp);
317 #endif
318
319 if (vdso_enabled == VDSO_DISABLED)
320 return 0;
321
322 down_write(&mm->mmap_sem);
323
324 /* Test compat mode once here, in case someone
325 changes it via sysctl */
326 compat = (vdso_enabled == VDSO_COMPAT);
327
328 map_compat_vdso(compat);
329
330 if (compat)
331 addr = VDSO_HIGH_BASE;
332 else {
333 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
334 if (IS_ERR_VALUE(addr)) {
335 ret = addr;
336 goto up_fail;
337 }
338 }
339
340 current->mm->context.vdso = (void *)addr;
341
342 if (compat_uses_vma || !compat) {
343 /*
344 * MAYWRITE to allow gdb to COW and set breakpoints
345 */
346 ret = install_special_mapping(mm, addr, PAGE_SIZE,
347 VM_READ|VM_EXEC|
348 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
349 vdso32_pages);
350
351 if (ret)
352 goto up_fail;
353 }
354
355 current_thread_info()->sysenter_return =
356 VDSO32_SYMBOL(addr, SYSENTER_RETURN);
357
358 up_fail:
359 if (ret)
360 current->mm->context.vdso = NULL;
361
362 up_write(&mm->mmap_sem);
363
364 return ret;
365 }
366
367 #ifdef CONFIG_X86_64
368
369 subsys_initcall(sysenter_setup);
370
371 #ifdef CONFIG_SYSCTL
372 /* Register vsyscall32 into the ABI table */
373 #include <linux/sysctl.h>
374
375 static ctl_table abi_table2[] = {
376 {
377 .procname = "vsyscall32",
378 .data = &sysctl_vsyscall32,
379 .maxlen = sizeof(int),
380 .mode = 0644,
381 .proc_handler = proc_dointvec
382 },
383 {}
384 };
385
386 static ctl_table abi_root_table2[] = {
387 {
388 .procname = "abi",
389 .mode = 0555,
390 .child = abi_table2
391 },
392 {}
393 };
394
ia32_binfmt_init(void)395 static __init int ia32_binfmt_init(void)
396 {
397 register_sysctl_table(abi_root_table2);
398 return 0;
399 }
400 __initcall(ia32_binfmt_init);
401 #endif
402
403 #else /* CONFIG_X86_32 */
404
arch_vma_name(struct vm_area_struct * vma)405 const char *arch_vma_name(struct vm_area_struct *vma)
406 {
407 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
408 return "[vdso]";
409 return NULL;
410 }
411
get_gate_vma(struct mm_struct * mm)412 struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
413 {
414 /*
415 * Check to see if the corresponding task was created in compat vdso
416 * mode.
417 */
418 if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
419 return &gate_vma;
420 return NULL;
421 }
422
in_gate_area(struct mm_struct * mm,unsigned long addr)423 int in_gate_area(struct mm_struct *mm, unsigned long addr)
424 {
425 const struct vm_area_struct *vma = get_gate_vma(mm);
426
427 return vma && addr >= vma->vm_start && addr < vma->vm_end;
428 }
429
in_gate_area_no_mm(unsigned long addr)430 int in_gate_area_no_mm(unsigned long addr)
431 {
432 return 0;
433 }
434
435 #endif /* CONFIG_X86_64 */
436